A conventional gravity-operated flush toilet has several basic components. The porcelain or china components include a bowl and a water tank mounted on top of a rear portion of the bowl. The bowl and tank are usually separate pieces bolted together to form a so-called two-piece toilet. Modern gravity-operated flush toilets are frequently made as a so-called one-piece toilet in which the bowl and tank are made as one continuous integral piece of china.
The plumbing components of a gravity-operated flush toilet include a fill valve in the tank which is connected to a water supply line, a flush valve surrounding a drain hole in the bottom of the tank that communicates with the bowl, and a flapper valve that normally closes and seals the flush valve. The plumbing components further include a control such as a pushbutton or lever mounted on a wall of the tank that moves a lever whose remote end is connected to the flapper valve for lifting the same.
In the experience of this inventor, a wide variety of two-piece flush valves are used in toilets of current manufacture, each of which is used with toilet tank openings ranging from 3.25 inches to 3.95 inches in diameter. It would, however, be advantageous to provide an original manufacture flush valve and an after-installation flush valve that is constructed as a 3.00 inch diameter flush valve that can be used universally with toilet tank openings within the range of diameters mentioned above. Also in the experience of this inventor, no single flush valve and flush valve assembly currently in the art provides use of a 3.00 inch diameter flush valve for use with such a wide range of toilet tank openings. It would also be advantageous, as part of a universal assembly to provide a gasket that allows this wide range of variability. In the experience of this inventor, such a gasket would need to be of a soft elastomeric material, such as that used in flapper valves of current manufacture, and would be capable of simple adaptation and modification to specific applications while ensuring a good seal between the gasket, the flush valve and the toilet tank opening, as well as with the opening to the bowl which sits directly beneath the toilet tank opening.